1. Field
Example embodiments may relate to information storage devices, for example, to information storage devices that use magnetic domain wall movement and/or methods of fabricating information storage devices.
2. Description of the Related Art
Non-volatile information storing devices include a hard disc drive (HDD) and a random access memory (RAM).
A general HDD is a device that may read and/or write information by rotating a magnetic recording medium in disk form and/or moving a reading/writing head above a magnetic recording medium. HDDs are non-volatile data storage devices that may be capable of storing 100 gigabytes (GB) of data or more and may be used as a storage device in computers.
A HDD may include moving mechanical systems. These mechanical systems may cause various mechanic faults if the HDD is moved or shocked, thereby decreasing mobility and/or reliability of the HDD. These mechanical systems may increase manufacturing complexity and/or costs of the HDD, increase power consumption, and/or generate noise. If HDDs are reduced in size, these problems associated with manufacturing complexity and cost may increase.
A flash memory, which is widely used, is an example of non-volatile RAM. However, the flash memory has drawbacks of slow reading and writing speeds and short life span. Due to the drawbacks of flash memory, new memory devices such as ferroelectric random access memory (FRAM), magnetic random access memory (MRAM), and phase change random access memory (PRAM) have been developed in limited numbers and a few have been commercialized. However, because flash memory, FRAM, MRAM, and PRAM all include a switching device in their each memory cell, it may be difficult to reduce the memory cell area. Also, these memories may have smaller storage capacities when compared to a HDD.
Therefore, as a method of solving the drawbacks of the conventional non-volatile information storing devices described above, research for developing new storage devices that are capable of storing larger amounts of data while not including moving mechanical systems and switching devices has been carried out. As an example of the new storage devices, an information storage device using magnetic domain wall movement was proposed.
Magnetic regions that make up a magnetic body may be called magnetic domains. A single magnetic domain has identical direction of magnetic moment. Size and magnetization direction of magnetic domains may depend on the property, shape, size of a magnetic material and on external energy.
A magnetic domain wall may be a boundary between magnetic domains having different magnetization directions and may be moved by a current and/or a magnetic field applied to a magnetic material. A plurality of magnetic domains having one magnetization direction may be formed in a magnetic layer of a desired width and thickness, and magnetic domains and magnetic domain walls may be moved using a current and/or magnetic field.
Applying the principle of moving magnetic domain walls to information storage devices, magnetic domains may be passed through pinned reading/writing heads by movement of a magnetic domain wall, thereby enabling reading/writing without rotation of recording medium.
Information storage devices using movement of a magnetic domain wall may store a larger amount of data and may not require moving mechanical systems, thereby having increased mobility and/or reliability, being more easily manufactured, and having lower power consumption.
In order to successfully operate information storage devices using movement of a magnetic domain wall, magnetic domain wall movement may need to be more stable.
To secure stability of a magnetic domain wall movement bit by bit, an example method of forming notches at a side of a magnetic layer, for example, forming lateral notches, may be used. Magnetic domain walls moving due to a current pulse at or above a critical value may be stopped at lateral notches. Magnetic domain walls may be moved by one bit at a time by a plurality of lateral notches formed uniformly at the magnetic layer.
It may be difficult to form fine-sized notches at a side of a magnetic layer, which may have a width of only several tens of nanometers. For example, if notches are formed at both sides of a magnetic layer having a width of about 50 nm, notches may be formed to have a width of about 15 nm, one third of the width of the magnetic layer. It may be difficult to realize such fine lateral notches by an exposure and etching technique. It may be difficult to form fine lateral notches to have uniform interval, size, and shape. If interval, size, and/or shape of lateral notches are not uniform, intensity of a magnetic field stopping the magnetic domain wall, for example, intensity of the pinning magnetic field may vary, and reliability of example information storage device may be lowered. Thus, it may be difficult to fabricate an information storage device including lateral notches using related art techniques.